Malaysian authorities raised an alert for a north-eastern state after the virulent H5N1 bird flu virus was found to have spread to poultry in more villages.

Some 24,000 birds have been culled in Kelantan state since the H5N1 strain was reported March 6 after several backyard poultry died.

Che Abdullah Mat Nawi, who heads Kelantan’s agricultural committee, said on Thursday (March 16) that free-range chickens reared by residents in 20 villages have been affected. He said the state is getting more manpower and resources to survey a wider area to contain the spread of the virus.

“The situation is getting more serious but it is not yet an emergency situation as there is no transmission of the virus from bird to human. We have raised the alert so that we can pool resources from different departments” to curb the spread of the virus, he told The Associated Press.

Che Abdullah said commercial bird farms in the state were not affected by the virus.

The H5N1 strain is highly contagious and linked by the World Health Organization to hundreds of deaths worldwide over the last decade.

Health director-General Noor Hisham Abdullah said health officials have screened more than 3,500 villagers in the affected areas. More than a dozen people showing bird flu symptoms tested negative for the virus, he said.

Veterinary officials told local media that the virus could have been due to cockfighting activities involving roosters from neighbouring countries.

Che Abdullah said officials believed the virus was imported but have not determined the cause of the outbreak.